Studies of the potential of tactile aids to provide speech information to hearing-impaired persons have to date focused primarily on whether these devices do indeed produce measurable speech perception benefits, and on the relative benefits provided by different kinds of tactile aids. Such studies, while important, do not address more fundamental questions regarding the specific aspects of the stimulus that influence the identifiability of speech sounds presented via tactile aids. Investigations of tactile processing capabilities for stimuli like those presented via tactile aids are necessary for determining stimulus aspects that lead to greater identifiability. A tighter coupling of basic processing considerations to tactile aid applications has promise for advancing our understanding of both areas. The primary area investigated in the present proposal involves the stimulus aspects that determine the identifiability of speech stimuli presented via tactile displays. Series of experiments examine variations in stimulus location, direction and extent of stimulus movement, perceived intensity, and temporal cues, both separately and in combination, to determine their relative salience in discriminability of stimuli presented via tactile aids. Models that quantify the contribution of each stimulus dimension will be constructed and evaluated. A different set of experiments approaches the same issue by correlating physical outputs of the tactile display with perceptual confusions for the same stimuli, to investigate physical aspects of tactile speech stimuli that contribute to identifiability. Finally, issues of device specificity are addressed by comparing performance for different tactile arrays on subsets of the tasks described above. Overall, the results of the proposed experiments should enhance. our understanding of tactile processing of complex stimuli, such as those presented via tactile speech aids, and should also provide guidance for improving designs for displaying speech information via tactile aids.